1. What is the USGS Rainfall Intensity Equation?

The USGS (United States Geological Survey) rainfall intensity equation calculates the rate of rainfall by dividing the total rainfall amount by the duration of the rainfall event. This simple calculation provides valuable information for hydrologic analysis and flood prediction.

2. How Does the Calculator Work?

The calculator uses the USGS rainfall intensity equation:

Where:

• \( Rainfall\ Amount \) — Total precipitation (inches)
• \( Duration \) — Time period of rainfall (hours)
• \( Intensity \) — Rainfall rate (inches per hour)

Explanation: The equation provides the average rainfall intensity over the specified duration, which is crucial for hydrological modeling and flood prediction.

3. Importance of Rainfall Intensity Calculation

Details: Rainfall intensity is a key parameter in hydrology used for designing drainage systems, predicting flood risks, and analyzing watershed behavior.

4. Using the Calculator

Tips: Enter rainfall amount in inches and duration in hours. Both values must be positive numbers. The calculator will compute the average intensity in inches per hour.

5. Frequently Asked Questions (FAQ)

Q1: Why is rainfall intensity important?
A: Intensity determines how quickly water accumulates, affecting runoff rates, erosion potential, and flood risks.

Q2: What are typical rainfall intensity values?
A: Light rain is <0.1 in/h, moderate 0.1-0.3 in/h, heavy >0.3 in/h. Extreme events can exceed 2 in/h.

Q3: How should duration be measured?
A: Use the time period over which the rainfall amount was collected, typically in hours for this calculation.

Q4: Are there limitations to this equation?
A: This provides average intensity only. For peak intensities during short periods within a storm, more detailed data is needed.

Q5: How is this used in engineering?
A: Engineers use intensity-duration-frequency curves to design stormwater systems that can handle specific return period storms.